Water S.A

Online ISSN: 0378-4738
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PARAMETERS OF THE KLAGSHAMN PLANT DURING THE OBSERVATION PERIOD
Article
An on-line settlometer has been presented which automatically records sludge settling curves. From this curve the sensor deduces the initial hindered settling velocity (Vs). In order to evaluate the information gathered by the sensor, the instrument was used at an information rich full scale waste water treatment plant (Klagshamn, Sweden). This plant consists of a primary sedimentation tank followed by a single sludge post denitrification activated sludge system operated with an external carbon source. With the sensor a diurnal pattern could be detected in Vs. This pattern was mainly caused by the diurnal change in the sludge concentration. Using the Vesilind equation it was possible to standardise Vs for the sludge concentration. The variation in the standardised Vs' was less than for the experimental Vs. Still it was possible to detect a decrease in Vs' on nearly daily basis. At two of these instances rising sludge was detected in the settlometer during the 35 minutes lasting sedimen...
 
Article
Copyright: 1994 Water Research Commission Stable isotopes of water in rainfall and streams in the Jonkershoek Valley were used to determine the relative contribution of new water (i.e. rain) during storm flow conditions. Significant differences between rain and stream isotopic signatures which facilitated the use of a mass balance equation to calculate the components of storm flow were found. Analyses indicated that < 5% of the storm flow comprised direct runoff. This suggests that the rapid response of these streams to rainfall is mainly due to displaced groundwater.
 
Article
Copyright: 2009 Water Research Council Woody invading alien plants, many of which are nitrogen-fixing legumes (Fabaceae family), are currently cleared in South African catchments to reduce water loss and preserve streamflow, and for the restoration of the ecosystem. This study tested the hypothesis that clearing invasive alien vegetation may disturb the vegetation-micro-organism-soil N cycling system by producing a large once-off input of fresh tree litter fall rich in N and by eliminating a large N sink. Three experimental plots were established at the Riverlands Nature Reserve (Western Cape, South Africa). A site invaded by Acacia saligna to be used as control; a site cleared of Acacia saligna; and a site with natural vegetation to be used as background. Nitrogen concentrations in soil and groundwater, volumetric soil water contents, root density and weather conditions were measured during 2007. Oxidised forms of nitrogen, in particular NO3-, were dominant in the system. Recharge and leachate were simulated with the HYDRUS-2D model and used as inputs into Visual MODFLOW to predict the spatial distribution of nitrate plus nitrite (NOx) in groundwater. NOx levels in soil and groundwater were higher in alien-invaded areas compared to fynbos-covered land. A quick release of NOx into groundwater was observed due to high residual N reserves in the rooting zone, decreased evapotranspiration and increased recharge in the treatment cleared of alien vegetation. In the long run, high NOx concentrations in groundwater underlying cleared land will last only until all the excess nitrogen has been leached from the soil. A decrease in NOx concentration in groundwater can be expected thereafter. Clearing land of alien invasive legumes may therefore have a beneficial effect by reducing groundwater contamination from NOx and reducing water losses in catchments.
 
Article
The aim of this project was to monitor variations and relationships between coliform and E. coli counts, the activities of their marker enzymes GAL and GUD, and temperature and pH over a period of 12 months in river samples obtained from the Eastern Cape, South Africa. Several polluted water samples were collected for direct coliform β-D-galactosidase (B-GAL) and Escherichia coli β-D-glucuronidase (B-GUD) assays and the membrane filtration technique. While all the samples showed enzyme activities, not all exhibited growth on CM1046 media. Variation in B-GAL activity (40%) was observed between November (highest activity month) and May (lowest activity month). The highest and lowest B-GUD activities were observed in the months of September and May/June, respectively. The sensitivity of the spectrophotometric assay method was indicated by a limit of detection (LOD) of 1 coliform forming unit (CFU)/100 mℓ and 2 CFU/100 mℓ for coliforms and E. coli, respectively. There was a significant (P < 0.05) positive correlation between E. coli counts and GUD activity (R2 = 0.8909). A correlation of R2 = 0.9151 was also observed between total coliforms and B-GAL activity, even though the CFUs were not evenly distributed. Direct enzyme assays were also shown to be more sensitive than the membrane filtration (MF) technique.
 
BROAD DESCRIPTION OF THE RIVER SEGMENTS IDENTIFIED FOR THE CROCODILE AND ELANDS RIVERS
THE CLASSIFICATION OF ECOLOGICAL INTEGRITY OF RIVERINE ECOSYSTEMS USED FOR THE ASSESSMENT OF RHP RESULTS
Map indicating preliminary geomorphological segments for the Crocodile and Elands Rivers
Article
The River Health Programme (RHP) is being designed to generate information regarding the ecological state of riverine ecosystems in South Africa. An adaptive assessment and management procedure is suggested as a means of linking the monitoring outcomes of the RHP with water resource management decisions. The potential of such a procedure is demonstrated, using data that have been collected, through the pilot application of the RHP, on the Crocodile and Elands Rivers, Mpumalanga. In order to assess the collected data relative to a reference state, homogeneous river segments were identified. Each segment was classified in terms of its relative ecological integrity, based on three biological indicators (fish, benthic invertebrates, riparian vegetation). These assessments of current integrity were compared with management goals and quality objectives for the respective river segments. Finally, river segments were ranked in terms of priority for receiving management attention, and an example is given of formulating appropriate management actions for addressing a high priority need. The systematic following of the step-wise procedure would facilitate and formalise the linking of data collection and assessment, the setting of management goals and quantifiable objectives, the selection of management options, and the monitoring of responses to chosen management actions.
 
Article
Copyright: 1993 Water Research Commission In a comprehensive study of the performance of a full-scale (45 m3) pure oxygen autothermal thermophilic aerobic reactor of a sewage sludge dual digestion system, it was found that: Biological heat generation rate was directly proportional to the biological oxygen consumption rate at 13,1 MJ/kgO; respiration quotient (mol CO2 generated per mol O2 consumed) was 0,66; vent gas was saturated with water vapour even at the high vent gas flow rates; COD and/or VS removal rates were poor parameters for quantifying the biological heat generation rate and controlling the reactor temperature. Increases in reactor temperature could be completely and virtually instantaneously controlled by means of the oxygen supply rate (OSR) for as long as the reactor was oxygen limited. The rapidity of response and close correlation between the oxygen transfer rate (OTR) and the biological heat generation rate make the OTR and the OSR pivotal parameters in the operation, control, design and simulation of oxygen limited autothermal thermophilic aerobic reactors in dual digestion.
 
Simulated operation conditions
Simulated and observed influent characteristics
Simulated nitrogen concentrations in the effluent at 10°C vs. aerobic time for an F/M ratio of 0.15 kg BOD 5 ·(kg MLVSS·d)-1
Article
The present study aims at optimizing the nitrification and denitrification phases at intermittently aerated process (activated sludge) removing nitrogen from municipal wastewater. The nitrogen removal performance recorded at 22 intermittently aerated plants was compared to the results obtained from the simulations given by the widely used ASM1. It is shown that simulations with a single value for the heterotrophic yield with any electron acceptor over-predict the nitrate concentration in the effluent of treatment plants. The reduction of this coefficient by 20% for anoxic conditions reduces the nitrate concentration by 10 g N·m-3. It significantly improves the accuracy of the predictions of nitrate concentrations in treated effluents compare to real data. Simulations with dual values (aerobic and anoxic conditions) for heterotrophic yield (modified ASM1) were then used to determine the practical daily aerobic time interval to meet a given nitrogen discharge objective. Finally, to support design decisions, the relevance of a pre-denitrification configuration in front of an intermittently aerated tank was studied. It is shown that when the load of BOD5 is below the conventional design value, a small contribution of the anoxic zone to nitrate removal occurs, except for over-aerated plants. When plants receive a higher load of BOD5, the modified ASM1 suggests that the anoxic zone has a higher contribution to nitrogen removal, for both correctly and over-aerated plants.
 
Review results at the review category, review area and report levels 
Sub-category quality review scores (shading to separate sub-categories per category) 
Article
In South Africa certain development activities, which may have a substantial detrimental effect on the environment, require an environmental impact assessment (EIA), including projects with the potential of affecting wetlands. A key element of the EIA process is the submission of an environmental impact report (EIR) for review in order to determine whether the report is adequate and/or whether a greater quantity of information is required before the project can be authorised. The information available to decision-makers in the EIR is a major determinant in the outcome of wetland protection and/or destruction. The quality of 4 environmental impact reports of large projects with the potential of impacting on wetlands was assessed using an EIA report quality review checklist. It is concluded that the quality of the 4 reports was generally satisfactory but certain areas were found to be poorly performed, i.e. identification and evaluation of impacts to the potential detriment of the wetlands for which the EIAs were performed To improve the quality of the reports for projects with the potential of affecting wetlands it is recommended that a quality review checklist be used by EIA practitioners and authorities as an additional tool to the EIA regulations and the integrated environmental management series. This should assist in ensuring that key aspects are addressed before submission to the relevant authority, and will also contribute to establishing a baseline of EIR quality for evaluation of wetlands EIA practice under the new regulations promulgated in 2006. http://search.sabinet.co.za/WebZ/Authorize?sessionid=0&next=ej/ej_content_waters.html&bad=error/authofail.html
 
Article
Mathematical models to predict runoff reductions due to afforestation are presented. The models are intended to aid decision-makers and planners who need to evaluate the water requirements of competing land uses at a district or regional scale. Five afforestation catchment experiments were analysed by the paired catchment method to determine the reductions in both total (annual) and low flows. The percentage reduction in flow after afforestation with both eucalypts and pines was determined for each post-treatment year relative to the expected flow based on a calibration relationship with an untreated (control) catchment. The authors fitted curves to these data points to predict the effects of afforestation under optimal and sub-optimal growing conditions. Eucalypt plantations were found to deplete both total and low flows sooner and in larger quantities than pine stands.
 
An illustration of groundwater separation from a hydrograph
Article
Copyright: 2002 Water Reearch Commission In South Africa, the flow requirements for maintaining the normal functioning of aquatic ecosystems is termed the “ecological reserve” and these should be determined when a licence application for water allocation is processed. Determination of the ecological reserve entails investigation of the relationship between the major interactive components of the hydrologic cycle, namely groundwater and surface water bodies including rivers, lakes and estuaries. Information on groundwater discharge towards surface water bodies is critical for the water resource manager to make a decision regarding the amount of groundwater allocation that can be licensed without causing a negative impact on aquatic ecosystems. Existing techniques of hydrograph-separation are too subjective either due to the fact that assumptions of the techniques cannot be met in reality or that the parameters used in models do not have physical meanings. This paper presents a geomorphologic framework under which the quantification of groundwater from a hydrograph is discussed. A focus is placed on hydrogeomorphological typing that can be used to guide a process of separating groundwater discharge time series from hydrographs where a monthly groundwater discharge time series is required for comparison with instream flow requirements. For generating monthly groundwater discharge time series, a generic procedure is proposed, which is applied in case study.
 
Article
The Limpopo Province in South Africa is richly endowed with thermal springs. Some have been developed for recreational, tourism or other purposes, while a number remain completely undeveloped. If the full economic potential of springs can be realised in a sustainable manner, they could make a substantial contribution to the local or even regional economy. The optimal use of a thermal spring is largely dependent upon its physical and chemical characteristics. This article focuses on the temperature and chemical features of 8 selected thermal springs located in the southern (Waterberg) region of the Limpopo Province, namely Warmbaths, Loubad, Vischgat, Die Oog, Rhemardo, Lekkerrus, Libertas and Buffelshoek. All of these springs are of meteoric origin, with water temperatures ranging from 30oC to 52oC. The mineral composition of the thermal waters reflects the geological formations found at the depth of origin. Changes in land use that occurred over the past few decades have apparently had no impact on the physical and chemical properties of the thermal spring waters. This effect may, however, become evident at a later stage due to a time lag in the migration of contaminants. The fluoride concentration of water from seven of the eight springs (all except Loubad) does not conform to domestic water quality guidelines and makes the water unfit for human consumption. Unacceptably high values of mercury were detected at Libertas. It is recommended that strict monitoring of the concentration of fluoride and other potentially harmful elements should be mandatory whenever the thermal spring water is used for bottling, domestic or full-contact recreational purposes. http://search.sabinet.co.za/WebZ/Authorize?sessionid=0&next=ej/ej_content_waters.html&bad=error/authofail.html
 
Map of South Africa showing location of sub-basins (quaternary catchments)
(continued) 
Comparison of simulated statistics based on original and transformed CPCAPC estimates
Article
Spatially interpolated rainfall estimates from rain-gauges are widely used as input to hydrological models, but deriving accurate estimates at appropriate space and time scales remain a major problem. In South Africa there has been a gradual decrease in the number of active rain-gauges over time. Satellite-based estimates of spatial rainfall are becoming more readily available and offer a viable substitute. The paper presents the potential of using Climate Prediction Center African daily precipitation climatology (CPCAPC) satellite-based datasets (2001-2006) to drive a Pitman hydrological model which has been calibrated using gauge-based rainfall data (1920-1990). However, if two sources of rainfall data are to be used together, it is necessary to ensure that they are compatible in terms of their statistical properties. A non-linear frequency of exceedance transformation technique was used to correct the satellite data to be more consistent with historical spatial rainfall estimates. The technique generated simulation results for the 2001 to 2006 period that were greatly improved compared to the direct use of the untransformed satellite data. While there remain some further questions about the use of satellite-derived rainfall data in different parts of the country, they do seem to have the potential to contribute to extending water resource modelling into the future.
 
The Mhlathuze River study area showing the positions of the six sampling sites
(above) Seasonal ordinations generated from data collected at Sites 2 to 6 for the duration of the study. SASS4, NTAXA, ASPT and HQI values were superimposed onto the MDS configurations of presence-absencetransformed family level data.
Description of codes and analyses used in this section
Comparison between the FAMILY [F] analysis and the TAXON [T] and ABUNDANCE [A] analyses respectively, across all sites
(right) Seasonal ordinations of community data at three different levels of detail, collected at Sites 2 to 6 for the duration of the study. Superimposed cluster groups were formed at a rank similarity cut-off of 30, unless otherwise stated in Table 6.
Article
The purpose of the study was to verify the ability of the South African Scoring System version 4 (SASS4), to assess the health of aquatic ecosystems. The macro invertebrate community attributes of the Mhlathuze River (KwaZulu-Natal, South Africa) were studied by applying the SASS4 rapid bioassessment method. In testing the effect of spatial and temporal variability in community structure on SASS4 scores it was found that there was a stronger spatial than a temporal effect. It was determined that of the indices used in association with SASS4, the biotic indices (average score per taxon, total score and number of tax) reflected changes in community structure, but the abiotic habitat quality index did not. It was found that qualitative family-level data provided an adequate classification of sites for use in routine biomonitoring. Ambiguous results were obtained with respect to the importance of measuring abundance during routine biomonitoring. No definite conclusion with respect to the ability of the SASS4 to reflect physical-chemical water quality changes could be drawn from the results obtained in this study. SASS4 was able to reflect the effect of the tidal push from the Mhlathuze Estuary, but this marine influence probably masked less pronounced effects exerted by the remainder of the physical-chemical variables that were investigated.
 
Correction factors used to adjust the concentrations of metals in estuarine and seawater samples of varying salinities 
Metal concentrations plotted against Fe, from clean baseline sediment samples. Linear regression lines and ± 95% prediction limits are superimposed on the data. Linear regression parameters and the linear equation are shown in bottom rights corner of each figure.
Mean (± SD) enrichment factors (EF) for sediments from the Kariega, East Kleinemonde and Riet Estuaries, sampled during dry and wet seasons 
Metal concentrations plotted against Fe for the Kariega Estuary sediments. Linear regression lines and ±5% prediction limits from clean sediments are superimposed on the data.
Article
The concentrations of select metals (Cd, Co, Cu, Fe, Pb, Ni and Zn) within the water column and sediment of the permanently open Kariega Estuary and temporary open / closed Riet and East Kleinemonde Estuaries were investigated during a dry and a wet season. Enrichment factors (EFs), using Fe as a reference element, and baseline linear regression models for metals vs Fe were used to assess the extent of metal enrichment in the sediments. The results of the study indicate that Cd, Co Ni and Pb were enriched above baseline concentrations (1.0 < EF < 4.1) in the sediments of all three estuaries. Co, Pb and Ni enrichment in the Kariega Estuary sediments was significantly higher during the dry season, and the mean concentrations of Pb and Cd in the water column were 19-fold and 66-fold higher in the dry season. The elevated concentration of metals during the dry season could be related to accumulation of diffuse pollution from human activities within the catchment area. Conversely, inflow of freshwater into the estuary had the net effect of reducing the concentration and enrichment of these metals within the Kariega Estuary due to scouring and outflow of estuarine water and sediment into the marine environment. The temporal variations in metal concentrations and enrichment factors were less pronounced in the temporary open / closed estuaries than the Kariega Estuary. The observed trend can probably be related to the low anthropogenic impact within the catchment areas of these systems, and the relatively smaller size of the catchments. Significant spatial variations existed in metal enrichment in the sediment of both the East Kleinemonde and Riet Estuaries, with the highest degrees of enrichment occurring in the sediments from the marine environment and lower reaches.
 
Article
Copyright: 2006 Water Research Commission The legal requirement for an Ecological Reserve established in South Africa’s water law is commonly regarded by stakeholders as being in direct competition with the needs of humans. This has resulted in much debate and varying interpretations of the meaning and purpose of the Ecological Reserve. However, the requirement for water that is allocated to sustain ecosystem functions is directly aligned with options for human use arising from rivers to deliver a suite of ecosystem goods and services to society. In this paper, we propose a conceptual approach to support a more constructive debate around the role and function of the Reserve in the sustainable use and protection of a suite of benefits to society. The approach proposes that debate be structured around managing for a dynamic ecological state in rivers that would in turn achieve the desired (albeit dynamic) mix of goods and services to a wide range of stakeholders. These stakeholders come from widely differing socioeconomic backgrounds, and their needs may be either for the direct use of water and associated resources located within the macro channels of rivers, or for their use in supporting social and economic activity remote from the river. The paper shows how goods and services concepts can provide an approach that contributes to developing a shared understanding that facilitates decisions on water allocations. The implication is that when water allocations can be evaluated comparatively it creates greater awareness of each other’s needs and interdependencies and value is attached to a greater diversity of benefits and costs. This in turn allows for opportunities to achieve more equitable recognition and allocation of the resources associated with rivers. The approach assists in making the conceptual link between goods and services that arise from constructed production systems, and those that arise from natural production systems (i.e. ecosystems). Off-site as well as on-site use of river goods and services (the latter being catered for by the Ecological Reserve) can in this way be brought into debate in a way that promotes wider appreciation of society’s diverse uses of river resources. In doing so it promotes interest-based participation as intended by legislation.
 
Mean (A) gill-net and (B) long-line catch per unit effort (CPUE) for experimental nets set in 10 dams of the North West Province of South Africa between April 2002 and February 2003. Error bars indicate standard error; numbers above error bars = sample size. Each net consisted of 5 randomly placed panels (3 m deep x 10 m long) with stretched mesh size of 44 mm, 60 mm, 75 mm, 100 mm and 144 mm. BOS = Bospoort, KOS = Koster, LIN = Lindleyspoort, LOT = Lotlamoreng, MAD = Madikwe, MOL = Molatedi, NGO = Ngotwane, ROO = Roodekopjes, TAU = Taung, VAA = Vaalkop.
CPUE by mesh size in experimental gill-net fleets set in 10 dams in the North West Province between April 2002 and March 2003 . BOS = Bospoort, KOS = Koster, LIN = Lindleyspoort, LOT = Lotlamoreng, MAD = Madikwe, MOL = Molatedi, NGO = Ngot- wane, ROO = Roodekopjes, TAU = Taung, VAA = Vaalkop. 
Article
In contrast to many other African countries, inland fisheries in South Africa are poorly developed and the fish populations in many of the country’s 3 000 major dams are under-utilised. While the primary purpose South Africa’s dams is to supply water for domestic and agricultural use, there has been an increasing realisation that their fish populations could make a contribution to food security through the establishment of capture fisheries. Historically, the fish in most South African dams have primarily been utilised for recreational fishing purposes, as subsistence use was criminalised by the apartheid regime in all waters except in the former homeland areas. This legacy persists as many of South Africa’s rural communities do not have a fishing tradition and there is a lack of an institutional framework to facilitate managed and sustainable access to the fish resource in inland waters. Current utilisation of many inland dams is often complicated by the existence of multiple authorities and interest groups, often with competing agendas. As a result, the economic potential of these water bodies is unknown and often grossly underutilised. Our study outlines a case study of fisheries resources in the North West Province of South Africa that could be used for the creation of income and food security for local communities through the development of subsistence, commercial, and recreational fisheries. The study identifies the lack of guidelines for the development of inland fisheries and the lack of an inland fisheries policy, both at the provincial and national level, as major bottlenecks for the sustainable development of these resources and outlines possible focal areas for intervention.
 
Article
In 1998, South Africa’s National Water Act (Act 36 of 1998) was promulgated to give legal status to the White Paper on a National Water Policy (April 1997) and the Department of Water Affairs’ (DWAF) water quality management policies and strategies, amongst others. To fulfil its legal obligation in terms of the management and control of land-derived wastewater discharges (classified as a water use under the National Water Act), DWAF adopted the operational policy for disposal of land-derived water containing waste to the marine environment of South Africa in July 2004 (the marine environment including estuaries, the surf zone and offshore waters) in July 2004; this policy incorporates relevant international and national principles, policies and legislation. The operational policy outlines the Department’s new thinking in relation to discharges to sea and consists of: A goal, Basic Principles, providing the broad reference framework or direction of the policy, Ground Rules, providing more specific rules, derived within the broader context of the Basic Principles, Management Framework, providing a generic, structured approach within which to implement the policy. This paper is to provide an overview on the Basic Principles and Ground Rules that were adopted under the operational policy.
 
ALIEN SPECIES AND ASSOCIATED BIOMASS EQUATIONS USED IN CALCULATING THE IMPACT OF INVADERS ON WATER RESOURCES. BIOMASS EQUATIONS ARE BASED ON SPECIES GROWTH FORM (SEE TABLE 2). DECIDUOUS SPECIES ARE INDICATED WITH # 
TOP 10 INVADING SPECIES OR GROUPS OF SPECIES IN SOUTH AFRICA RANKED 
Article
The impacts of the widespread invasions by alien plants in South Africa are increasingly recognised. Most of the past concern has been about the impacts on conservation areas, other areas of natural vegetation and on agricultural productivity. The potential impact of invading alien woody plants on water resources was known to be serious but there has been no information available to evaluate the significance of these water losses across the whole country. This paper reports on the results of a preliminary survey aimed at obtaining an overview of the extent, impacts and implications of alien plant invasions at a national and regional level for South Africa and Lesotho. Data on the extent and location of the invaded areas were obtained from a variety of sources including detailed field mapping, mainly at a 1:250 000 scale with some at 1:50 000 and 1:10 000, and generalised information on species and densities. The density class of each species in each polygon was mapped and used to derive the condensed areas (the equivalent area with a canopy cover of 100%). Each of the invading species was classified as a tall shrub, medium tree or tall tree - based on growth form and likely water use - and its biomass was estimated from a function based on vegetation age. The incremental water use (i.e. the additional water use compared with the natural vegetation) was calculated using the following equation: Water use (mm) = 0.0238 x biomass (g/m (2)) which was derived from catchment studies. Alien plants, mainly trees and woody shrubs, have invaded an estimated 10.1 million ha of South Africa and Lesotho, an area larger than the province of KwaZulu-Natal. The equivalent condensed area is 1.7 million ha which is greater than the area of Gauteng Province. The Western Cape is the most heavily invaded at about a third of the total area, followed by Mpumalanga, KwaZulu-Natal and Northern Province. The catchments of the Berg and Breede Rivers are the most heavily invaded followed by the George-Tsitsikamma region, Port Elizabeth coastal region and the Drakensberg escarpment in Mpumalanga. The total incremental water use of invading alien plants is estimated at 3 300 million m(3); of water per year, equivalent to about 75% of the virgin MAR of the Vaal River system. About a third of the estimated total water use, by volume, is accounted for by alien invaders in the Western Cape, followed by KwaZulu-Natal (17%), the Eastern Cape (17%) and Mpumalanga (14%). The greatest reduction as a percentage of MAR was found in the arid Northern Cape (17%), followed by the Western Cape (15%) and Gauteng (10%). For primary catchments, the greatest percentage reductions were in the Namaqualand coast (catchment F, 91%) followed by the Eastern Cape Coast (P, 42%) and the south-western Cape (G, 31%). The extent and density of the invasions and thus the impact on water resources could increase significantly in the next 5 to 10 years, resulting in the loss of much, or possibly even all, of the available water in certain catchment areas. Alien plant control is expensive but it has been shown that control programmes are cost-effective compared with alternative water supply schemes. This preliminary assessment needs to be interpreted with caution because the results are based on a data set that contains some important uncertainties. The water-use estimates also involve some critical assumptions. Nevertheless, the scale of the invasions, the magnitudes of the impacts and the rapid expansion we are observing are such that a national control programme is essential if the country's water resources are to be protected.
 
Article
The Orange River, South Africa's largest river, is a critical water resource for the country. In spite of the clear economic benefits of regulating river flows through a series of impoundments, one of the significant undesirable ecological consequences of this regulation has been the regular outbreaks of the pest blackfly species Simulium chutteri and S. damnosum s.l. (Diptera: Simuliidae). The current control programme, carried out by the South African National Department of Agriculture, uses regular applications, by helicopter, of the target-specific bacterial larvicide Bacillus thuringiensis var. israelensis. While cost-benefit analyses show significant benefits to the control programme, benefits could potentially be further increased through applying smaller volumes of larvicide in an optimised manner, which incorporates upstream residual amounts of pesticide through downstream carry. Using an optimisation technique applied in the West African Onchocerciasis Control Programme, to a 136 km stretch of the Orange River which includes 31 blackfly breeding sites, we demonstrate that 28.5% less larvicide could be used to potentially achieve the same control of blackfly. This translates into potential annual savings of between R540 000 and R1 800 000. A comparison of larvicide volumes estimated using traditional vs. optimised approaches at different discharges, illustrates that the savings on optimisation decline linearly with increasing flow volumes. Larvicide applications at the lowest discharge considered (40 m3·s-1) showed the greatest benefits from optimisations, with benefits remaining but decreasing to a theoretical 30% up to median flows of 100 m3·s-1. Given that almost 70% of flows in July are less than 100 m3·s-1, we suggest that an optimised approach is appropriate for the Orange River Blackfly Control Programme, particularly for flow volumes of less than 100 m3·s-1. We recommend that trials be undertaken over two reaches of the Orange River, one using the traditional approach, and another using the optimised approach, to test the efficacy of using optimised volumes of B.t.i.
 
Article
Since the South African Department of Health has tabled legislation to make fluoridation of public water supplies mandatory, the issue of whether fluoride is beneficial or harmful has, once again, become controversial in South Africa. We reviewed the literature, the experiences of fluoridation in overseas countries and the latest WHO recommendations, and have found that fluoride is desirable at certain levels, and undesirable above these. The following recommendations are made for optimum fluoride levels in South Africa's potable water: The decision to fluoridate a public water supply must be a community decision taken after public consultation. However, it can only be reached when the public is properly informed about the issue. Optimum levels of fluoride for human health range from 0.4 to 0.7 mg F/l, depending on the maximum mean annual temperature. The maximum level of 0.7 mg F/l should not be exceeded. Accordingly, it is recommended that in areas where natural fluoride concentrations in the drinking water exceed 0.7 mg F/l steps be taken to defluoridate the water. As an interim measure, a scale of temperature-adjusted optimum fluoride levels should be adopted in South Africa, rather than a single level covering the wide-ranging ambient temperatures (and corresponding consumption rates of drinking water) in the country. A sliding scale would mean that the community within a water supply region can determine its own fluoride consumption within the optimum range. Fluoridation should be considered only a short-term measure, until economic conditions are such that all South Africans have access to proper dental health care. The duration of fluoridation of a community water supply, and the level of fluoridation (within the optimum range of fluoride levels) should both be considered community decision. However, defluoridation should be a permanent necessity in those areas where the drinking water exceeds levels of 0.7 mg F/l.
 
River segmentation into completely mixed tank in series (CMTS)
Article
Copyright: 2003 Water Research Commission Using a simple conceptual dynamic river water quality model, the effects of different basin-wide water quality management options on downstream water quality improvements in a semi-arid river, the Crocodile River (South Africa) were investigated. When a river is impacted by high rates of freshwater withdrawal (in its upstream reaches), and receives polluted side-stream inflows and wastewater effluent discharges (in the middle reaches), river water quality can deteriorate seriously over time. This study focusedon two water quality problems: Progressive increases in the concentrations of total dissolved solids (TDS) as a measure of salinity, and the concentrations of nitrate-plus-nitrite and ammonia (as inorganic nitrogen) as a measure of eutrophication. Based on a low flow analysis for the period prior to construction of the Kwena Dam (1960 to 1979), the 7d low flows that could be expected to occur every 10 years (7Q10) are generally very low (< 0.5 m3•s-1), both in the upstream (Montrose Weir) and the downstream (Kruger National Park) sections of the Crocodile River. During such critical periods of low river flow, very low effluent standard limits would be required to prevent adverse river water quality. However, these options are not economically feasible. Furthermore,inflows from the highly polluted tributary stream, the Kaap River, which drains an area where considerable gold mining takes place, govern water quality in the Crocodile River downstream of the Crocodile-Kaap confluence. Subsequently, two additional water quality control options (setting limits for maximum water withdrawal and low-flow augmentation) were analysed. The results show that a decrease in maximum water withdrawal could reduce the TDS concentration. Furthermore, controlling water release patterns from a dam at the Montrose Weir can have a remarkably positive effect on the downstream river water quality. On the basis of the 1989/90 monitoring data, a minimum flow of 5 m3•s-1 at the Montrose Weir can reduce concentrations of TDS and ammonia nitrogen by about 20% and 60%, respectively, in the Kruger National Park (at the downstream point of the considered river).However, this management option does not reduce nitrate nitrogen concentrations. The proposed model used in this study is relatively simple and can be used as a tool for the evaluation of short-term (monthly) basin-wide water quality management options.
 
Article
There is a need in South Africa for institutional innovations aimed at increasing the coverage of water services, and sustaining those services. The paper describes an investigation of an alternative service delivery institutional concept, viz. the franchising of the operation of water services, and outlines the need to formulate a franchise model that could be developed and made available to emerging entrepreneurs as the basis of a viable business. The franchising would be in respect of components of the water services value chain that are suitable for small businesses in that they can be readily systematized.
 
Article
Forestry is an important sector of industry in South Africa but the growing of timber places significant demands on the available water resources. Yet, a ready source of information on the extent, and probable hydrological impacts, of afforestation in specific locations in South Africa has not been available. This paper reports on the modelling exercise conducted to produce an easy-to-use, handy catalogue to fill this need, and presents some of the notable results of this exercise. Databases of quaternary catchment and magisterial district boundaries, rainfall, streamflow, forestry areas by tree genus, timber rotation lengths (years) and forestry growth potential were combined by means of a geographical information system to delineate uniform blocks of forestry. On these blocks a robust empirical model predicted total and low-flow reductions as a function of rotation, length, tree genus, water availability, growth potential and plantation age distribution. The results were summarised by quaternary, tertiary, secondary and primary catchment, and by magisterial district and province. The area of commercial timber plantations in South Africa is estimated at 1.5 million ha (57% pine, 35% eucalypts and 8% wattle), covering just 1.2% of South Africa. But the regions in which forestry is concentrated receive higher rainfall and yield a disproportionately large share of the streamflow, particularly low flow (dry-season flow). The commercial plantations are estimated to reduce mean annual streamflow by 3.2% (1417 x 10(6) m(3)) and low flows by 7.8% (101 x 10(6) m(3)/yr). Our estimate of an average reduction of 98.6 mm/yr per unit of planted area is 13% lower than the previous nation-wide estimate (113.6 mm/yr) of the net effect of forestry on total water resources (DWA, 1986). Mpumalanga Province with the highest concentration of forestry (7.2% of land area) experiences the largest reductions in flow - almost 10% of total flow and 18% of low flows. However, the largest relative impacts on low flow are seen in Northern Province where small areas of forestry are confined to humid upper catchments that are the principal source of dry-season flow in otherwise dry secondary catchments.
 
Article
This paper discusses the long-term implementation of the South African National Water Policy of 1997, and addresses some of the difficult issues of the management and leadership of large change processes. Although the vision established by the water policy is clear, actually achieving that vision on the ground will require a robust, flexible, long-term implementation plan that is supported by all the role players responsible for water management in South Africa: Government, water services authorities, water services providers such as water boards, catchment management agencies (CMAs) water user associations, research organisations and the private sector. In this paper, we advocate a strategic, adaptive approach to policy implementation, which equates to "learn-by-doing", to meet the challenge of maintaining sufficient forward momentum in policy implementation, while still making sound decisions that take account of technical, environmental, economic, social and political factors.
 
Whitfield's (1992) physical classification of estuaries
Estuarine habitats and total areas for incorporation in the habitat rarity score, based on cover data for 92% of the country's estuaries (Colloty, 2000)
Calculation of the biodiversity importance score
Article
The future health and productivity of South Africa's approximately 250 estuaries is dependent on two main factors; management and freshwater inputs. Both management and water allocation decisions involve trade-offs between conservation and various types of utilisation. In order to facilitate decision-making in both of these spheres, it is necessary to understand the relative conservation importance of different estuaries. This study devises a method for prioritising South African estuaries on the basis of conservation importance, and presents the results of a ranking based on the collation of existing data for all South African estuaries. Estuaries are scored in terms of their size, type and biogeographical zone, habitats and biota (plants, invertebrates, fish and birds). Thirty-three estuaries are currently under formal protection, but they are not representative of all estuarine biodiversity, We performed a complementarity analysis, incorporating data on abundance where available, to determine the minimum set of estuaries that includes all known species of plants, invertebrates, fishes and birds. In total, 32 estuaries were identified as 'required protected areas', including 10 which are already protected. An estuary's importance status (including 'required protected area' status) will influence the choice of management class and hence freshwater allocation under the country's new Water Act, and can be used to assist the development of a new management strategy for estuaries, which is currently underway.
 
Abiotic characteristics of 16 sites from South Africa a and Namibia b from which adult Artemia and/or Artemia cysts were collected during July/August 2003 
Salt pans, salt works and lakes in East and Southern Africa with salinity values known to be greater than 40 g·ℓ –1 (some sites have water only seasonally) 
Article
Brine shrimp (genus Artemia) are small (8 to 12 mm long) cosmopolitan crustaceans (Anostraca) found predominately in hypersaline water bodies such as inland salt lakes and pans, coastal lagoons, and salt works at salinity levels above 40 g(.)l[superscript(-1)]. They have been extensively studied due to their high monetary value as food for larval fish in aquaculture and their unique reproductive strategies. Brine shrimp occur as either bisexual species or as parthenogenetic populations. Despite published reviews of their world-wide distribution little is known about their occurrence in Africa. This review adds new information about 70 African Artemia sites and lists 26 potential sites and their coordinates. Sixteen sites in Southern Africa and Namibia were visited during a collecting trip, and new information on the reproductive mode of nine of these sites is given. Several South African populations exhibit bisexual reproduction. In Namibia there are two parthenogenetic populations (Walvis Bay and Swartkops) and an additional bisexual population (Hentie's Bay). A mixed population (bisexual and parthenogenetic reproduction at the same site) was found at Coega, South Africa.
 
Article
The Kariega Estuary is a freshwater-deprived system due to numerous impoundments in the catchment. This system has had little or no horizontal salinity gradient over the last 15 years, with hypersaline conditions sometimes predominating in the upper reaches. Following high rainfall events in the catchment during the spring of 2006, including a flood event (approximate 1:10 year) in August 2006, a series of riverine pulses entered the estuary and a horizontal salinity gradient was established. This study examined the influence of this freshwater pulse on four components of the biota within the estuary, namely the zooplankton, and larval, littoral and demersal fishes. The study demonstrated that in three of these components elevated densities were recorded following the riverine input, with only the littoral fishes retaining an almost constant density. In addition, changes in the relative contributions of the estuarine utilisation classes for all three fish groups examined indicated that freshwater input into these systems positively influences the abundances. This has significant implications for water managers as it demonstrates the importance of an Ecological Reserve (defined as ‘the water required to protect the aquatic ecosystems of the water resource’) for this system.
 
Some of the characteristics of uncertainty and variability with particular reference to ecological models (based on Frey, 1993 and USEPA, 1997) 
Article
The principle of ecosystem protection in the South African Water Act requires that water resource management tools for a multiple stressor environment be tailored to the characteristics of the aquatic ecosystem. The requirements of the Act, the characteristics of aquatic ecosystems as well as co-occurrence of diverse stressors are considered. Although single substance criteria have a useful role, they are not sufficient for resource management within the context of the ecological reserve. It is proposed that an effect-likelihood approach has the potential to address the variability and uncertainty in management of a surface water body subject to multiple stressors. An in-stream receiving water risk objective approach might be considered.
 
The fundamental components of a strategic adaptive management system
A framework for institutionalising strategic adaptive management
An interpretation of the management cycle for implementing the new South African Water Act
Article
Copyright: 2000 Water Research Commission Catchment management agencies (CMA's) have no tested precedent in South Africa and will have to evolve in complex and changing business, social and natural environments as they strive to ensure that equity and social justice are achieved within ecological limits. Traditionally, very different styles of management have been used for resource exploitation and resource protection and this will present a serious dilemma for CMAs. As the human population has grown and natural resources have declined, there has been increased effort to control nature in order to harvest its products and reduce its threats. Initially such "command-and-control" management has been successful as agencies prosper on short-term gains. However, when natural variation is reduced the ecosystem loses its resilience and ability to "bounce back" from disturbances. The first lesson learnt is that the longer term consequence of command-and-control management is always either a reduction or cessation of resource supply. The second lesson comes from adaptive resource management (ARM). ARM acknowledges that, because nature is in a continual state of flux and our understanding of ecosystem functioning is poor; a fundamental problem for decision makers is that they must deal with uncertainty from an imperfect knowledge base. A learning-by-doing approach becomes a prerequisite for effective management. Unfortunately, there has been a tendency to superimpose adaptive management on bureaucratic institutional structures. Such flouting of the fundamental management axiom "form must follow function", has thwarted many attempts at adaptive management. This provides the third lesson. Recognition that authoritarian, command-and-control, bureaucracies respond too slowly to survive in changing environments has led managers in government, industry and businesses to create "learning institutions" which combine adaptive operations and generative leadership (lesson four). Effective knowledge management is seen as a critical success factor in turning command-and-control management into adaptive, learn-by-doing management (lesson five). CMAs which recognise the dangers of excessive command and control, the need to integrate stakeholder values and activities, and the potential of an adaptive and generative management approach, will need to structure its activities carefully. At present there is much focus on the structure of CMAs and much less on how they should function. Form is preceding function in many instances. When function is discussed it centres on how regulatory mechanisms and permit systems will keep resource use under control. The concern is seldom with how the ecosystem will be managed. This sort of thinking could lead to a classic command-and-control management approach if not tempered with a more adaptive process. Strategic adaptive management (SAM) is a local derivative of ARM designed to generate consensus management which is inclusive, strategic, adaptive and creative. SAM is a process in which effective knowledge management is central to building a partnership between science, management and society to achieve a common vision. It has considerable potential for application to CMAs.
 
Actions in analysis plan formulation
Actions in analysing information
Article
In order to facilitate a common understanding, on-going debate and increasing application of ecological risk assessment (ERA) in South Africa, the ERA process of the US Environmental Protection Agency (EPA) has been summarised and evaluated for South African conditions, Many of the individual steps in the process have been interpreted and reworded in order to improve communication of the concepts. The basic process is unchanged though a few minor changes are recommended as improvements. A comparison is also made with integrated environmental management (IEM). It is noted that ERA addresses many of the key principles underpinning IEM, including consultation with interested and affected parties which provides an opportunity for public and specialist input into the decision-making process. However, there are some differences though more in degree than in principle. Of importance is that the ERA framework provides explicitly for quantification of all aspects of an assessment in an IEM procedure.
 
Article
A case study is presented where the feasibility of bioventing was assessed for the remediation of a petroleum-contaminated site. This was achieved through the determination of the radius of influence of a single vent well, the soil gas permeability of the site and the oxygen utilisation rate of the in situ micro-organisms. The on-site test used one vent well and three monitoring wells. A radius of influence of 9.5 m was determined. A soil gas permeability of 3.8 Darcy was measured. The oxygen utilisation of 1.32% (v/v) O-2/h indicated that an active microbial population existed in situ. The theoretical biodegradation rate was calculated to be 752 mg hydrocarbon (based on hexane)/kg soil-month. Based on these results, bioventing was found to be a feasible bioremediation option for cleanup of the site, provided that other soil conditions were suitable for biological activity.
 
The study site showing Subcatchment No. 18 of the Midmar catchment in the KwaZulu-Natal midlands, South Africa
A COMPARISON OF THE COST OF DIFFERENT REMOTE SENSING TECHNIQUES
Article
It has been estimated that South Africa will reach the limits of its usable freshwater resources during the first half of the next century if current trends in water use are not reversed. Removing alien vegetation, responsible for the uptake of large amounts of water from riparian zones, is one of the methods of maximising water supply in South Africa. Remote sensing is a cost- and time-effective technique for identifying alien vegetation in riparian zones and remote sensing data can be incorporated into a geographic information system (GIS) which can be used as a tool for the management of riparian zones. In this paper, vegetation identification and classification techniques by using aerial videography, aerial photography and satellite imagery, are assessed in terms of accuracy and cost for a small subcatchment in the KwaZulu-Natal midlands. This was achieved by incorporating the data obtained from aerial videography, aerial photography and ground mapping into a GIS. Accuracies of the different techniques were then examined. Data obtained from satellite imagery were assessed independently using digital image decoding procedures. The costs of each technique were also determined and, together with the accuracy results, used to make recommendations for the most effective manner of identifying alien vegetation in riparian zones. The accuracy results obtained in this study indicate that using manual techniques to identify riparian vegetation from 1:10 000 black: and white aerial photographs yield the most accurate and cost-effective results. The least cost-effective data sources were found to be 1:10 000 colour aerial photographs and digital aerial photographs and the least accurate data sources were aerial videography and Landsat thematic mapper (TM) satellite imagery.
 
Combined May and October electro-fishing survey sites for Chiloglanis sampling within the Sabie catchment, together with location of water temperature survey sites. Points A-B refer to a critical thermal reach for C. anoterus within the Sabie River, which is 128-138 km downstream from the top of the catchment. 
Box-and-whisker plot of condition factor (mass to length ratio) of C. anoterus adults vs. site, based on pooled data from electro- fishing surveys listed in Fig. 5. Whiskers show maximum and minimum values, while the box shows the middle 50% of the data, with the median shown as a line within the box. 
Article
Adaptive management of river systems assumes uncertainty and makes provision for system variability. Inherent within this management approach is that perceived limits of 'acceptable' system variability are regarded not only as testable hypotheses, but also as playing a central role in maintaining biodiversity. While the Kruger National Park currently functions as a flagship conservation area in South Africa, projected increases in air temperatures as a consequence of global climate change present challenges in conserving this biodiversity inside the established land boundaries. Within the rivers of the Kruger National Park, a management goal of maintaining biodiversity requires a clearer understanding of system variability. One component of this is water temperature, an important water quality parameter defining the distribution patterns of aquatic organisms. In this study, Chiloglanis anoterus Crass (1960) (Pisces: Mochokidae) was selected as a biological indicator of changes in annual water temperatures within the Sabie River in the southern Kruger National Park. Relative abundances of C. anoterus were determined using standard electro-fishing surveys. The presence or absence of C. anoterus was linked to cumulative annual heat units using a logistic regression model, and a critical annual cumulative water temperature threshold estimated. A correlative relationship between this temperature threshold and a biological index using a C. anoterus condition factor provides river ecologists with a tool to assess ecologically significant warming trends in Sabie River water temperatures. A similar approach could be applied with relative ease to other Southern African river systems. Further testing of this hypothesis is suggested, as part of the adaptive management cycle.
 
Organic priority pollutants (after Schleyer et al., 1992)
Article
Copyright: 2004 Water Research Commission Groundwater pollution is a worldwide phenomenon with potentially disastrous consequences. Prevention of pollution is the ideal approach. However, in practice groundwater quality monitoring is the main tool for timely detection of pollutants and protection of groundwater resources. Monitoring groundwater quality is a specialized task for a hydrogeologist and a water quality monitoring expert. Although general prescriptions for waste management facilities exist these may not be applicable in all cases. In the literature, divergent approaches have identified various sets of pollutants and pollution indicators. This paper discusses international and local trends in groundwater monitoring for baseline studies and on-going pollution detection monitoring for a variety of situations. Cemeteries, a pollution source for which no local monitoring requirements exist, are also included. The effectiveness of some commonly prescribed monitoring parameters is considered, as well as the use of “bulk parameters” for reducing the number of analyses and the associated costs, while still achieving the optimum result. Although not considered in detail in this paper, cost-effective groundwater quality monitoring should be a key part of the design of a monitoring programme.
 
Article
copyright: 2005 Water Research Commission Judicious management of a groundwater system requires an understanding of its hydrogeology and response to various recharge and pumping stresses. However, in developing countries, groundwater resource evaluations are hampered by a lack of adequate data that will allow for its complete characterisation. Under such circumstances it is not uncommon for ad hoc groundwater management measures to be embarked upon, especially during drought conditions. These were the conditions that existed during the 1991/92 drought when the CSIR Stellenbosch evaluated the groundwater resources of an urban aquifer in Bulawayo, Zimbabwe. Their recommendations revealed that about 3.5x10(6) m(3)/a could be safely abstracted from the aquifer. In this work, a more comprehensive hydrogeological investigation was carried out which included pumping tests, estimation of abstraction rates and recharges, and numerical modelling of the aquifer. The investigations indicate that the aquifer is unconfined with hydraulic conductivity and specific yield ranging from 0.1 m/d to 2.09 m/d and 0.02 to 0.11, respectively. Recharge estimates indicate an annual recharge of 105.5 mm with 38.4%, 52.1% and 9.5% accounting respectively for direct recharge, water mains and sewer leakages. Furthermore, a long-term sustainable annual abstraction of 6.1x10(6) m(3) or 15% of current city water demand can be obtained from the aquifer.
 
Pesticides used in the study area with their type of use and their physico-chemical properties
scenario parameter values of the water body defined to calculate 1 st tier ETR values using PRIMET
Article
External agricultural inputs, such as pesticides, may pose risks to aquatic ecosystems and affect aquatic populations, communities and ecosystems. To predict these risks, a tiered approach was followed, incorporating both the PRIMET and PERPEST models. The first-tier PRIMET model is designed to yield a relatively worst-case risk assessment requiring a minimum of input data, after which the effects of the risks can be refined using a higher tier PERPEST model. The risk assessment initially depends on data supplied from local landowners, pesticide characteristic, application scheme and physical scenario of the environment under question. Preliminary results are presented, together with ecotoxicological data on several frequently-used pesticides in a section of the Crocodile (west) Marico Water Management Area (WMA) in South Africa. This area is historically known to have a high pesticide usage, with deltamethrin, aldicarb, parathion, cypermethrin and dichlorvos being the main pesticides used. Deltamethrin was indicated as having the highest probability of risks to aquatic organisms occurring in the study area. Cypermethrin, parathion, dichlorvos, carbaryl, romoxynil, linuron, methomyl and aldicarb were all indicated as having possible risks (ETR 1-100) to the aquatic environment. Pesticides posing no risk included fenamiphos, abamectin, pendimethalin, captan, endosulfan, alachlor, bentazone and cyromazine (ETR
 
The Groot Marico and Molopo River systems (North West Province, South Africa) showing the location of the study area 
Descriptive statistics of water quality variables
Article
Two main approaches have been followed in using diatoms as bio-indicators in the past few decades namely species diversity indices and aut-ecological indices. This study, based on 102 water quality and epilithic diatom samples from the Crocodile Groot-Marico catchment in South Africa, evaluated both types of indices by establishing how well they reflect changes in water quality. It was found that less of the variation in diversity indices could be attributed to changes in water quality variables than was the case for the aut-ecological indices. Furthermore it was found that species diversity indices tend to be higher at intermediate levels of pollution, rather than at low levels of pollution.
 
Article
Copyright: 2006 Water Research Commission This paper presents an automated desktop procedure for delineating river longitudinal profiles into macro-reaches for use in Ecological Reserve assessments and to aid freshwater ecosystem conservation planning. The procedure was developed for use where there are limited data and/or where a repeatable, statistically defensible regional or national assessment is required. The delineation of longitudinal profiles into macro-reaches between 'controls' or 'break points' such as exposed resistant rock formations, knick points, or significant changes in lithology provides the initial coarse filter for further assessment of lower levels of organisation, channel type for example. The division is necessary, as research has demonstrated that not all macro-reaches respond in the same way to disturbance or stress, nor do they have the same biotic assemblages. Four statistical methods (Von Neumann mean square error, CUSUM plots or unweighted values and the Worsley Likelihood Ratio Test (WLRT)) were used to define macro-reach breaks for four South African rivers (Crocodile, Olifants, Mhlathuze and Seekoei Rivers) and were compared to previously defined macro-reach delineations based on expert-driven approaches. Results indicate that the CUSUM and WLRT approaches most closely match the macro-reach breakpoints as defined by the expert-driven approach. An automated desktop procedure was developed for computing statistically defensible, multiple change points along profiles using an adaptation of the WLRT method. The adapted approach does not require an a priori knowledge of the break points, as is the case in other applications of the WLRT. It is concluded that the adapted WLRT approach can be used with a reasonable degree of certainty where there are insufficient data and/or where a regional or national assessment is required that is repeatable and statistically defensible. Where possible, however, there is no substitute for primary data collection, field work and a detailed expert-driven approach.
 
Study catchments
Article
The paper describes a simple technique for baseflow separation from continuous monthly streamflow records which are widely available in South Africa. The technique employs a digital filter algorithm, which has been previously used only with more detailed daily streamflow records. The example applications of the separation technique in three gauged catchments are illustrated and its possible applications in the context of groundwater and estuarine components of the ecological reserve determination are discussed.
 
Gantt chart showing the production schedule 
Data used for the illustrative example 
Article
Copyright: 2008 Water Research Council Wastewater minimisation in chemical processes has always been the privilege of continuous rather than batch plants. However, this situation is steadily changing, since batch plants have a tendency to generate much more toxic effluent compared to their continuous counterparts which are usually encountered in bulk manufacturing. Past methodologies for wastewater minimisation in batch processes have focused on operations based on mass transfer. Consideration is not taken to the reuse of wastewater as part of product formulation. Reusing wastewater in product formulation has the major advantage of negating much of the effluent produced, thereby enabling a process to operate in an almost zero-effluent manner. Presented in this paper is a mathematical technique for the simultaneous design and scheduling of batch operations operating in a near-zero-effluent manner. The technique determines the number and size of the processing vessels, while ensuring maximum water reuse in product. The technique was applied to an illustrative example, and an 80% savings in wastewater was achieved, with a corresponding plant design that achieves the required production.
 
Article
The hydrodynamics and water quality of the Great Berg Estuary were studied under river flow conditions typical of the winter and summer seasons. Results reflect a strongly seasonal regime with the estuary exhibiting fluvial dominance during winter and marine dominance under the low-flow conditions of summer. Limited renewal of estuarine water occurs over the summer period with the result that a plug of characteristically estuarine water is formed. Tidal influence extends 69 km upstream of the mouth in summer, while salinities in excess of 5 x 10(-3) occur 37 km from the mouth. The role of river flow in counterbalancing the upstream dispersion of salt during the summer season is highlighted. The relevance of these findings in the preliminary assessment of the freshwater requirements of the Great Berg Estuary is addressed.
 
Article
Copyright: 2000 Water Research Commission The impact of biofilms present in water distribution systems on the microbial quality of potable water is reported in this review. The issues covered include the composition of biofilms, factors governing their formation and the effect and significance of biofilms on the microbial quality of drinking water. The review addresses the main factors governing the formation of biofilms such as the types of disinfectants and residual concentrations, resistance of bacteria to disinfectants, the influence of piping material and the effect of temperature. Methods for the enumeration of bacteria in biofilms as well as emerging technologies for in situ monitoring of biofilms are discussed. Suggested control measures for managing and controlling the problem of biofilm formation in potable water distribution systems to ensure potable water of an acceptable microbiological quality are dealt with.
 
Schematic of the bioreactor design for the removal of nitrogenous compounds from metal-processing wastewater
Influent and effluent pH 
Nitrate concentrations in the process influent and effluent and nitrite concentration in the effluent
Article
Although several nitrification/denitrification processes are established for the removal of ammonia and nitrate from municipal and industrial wastewaters, there are few reported results on the removal of these ions from metal-processing and finishing wastewaters. Unlike municipal wastewater, there is very little organic content in metal-processing wastewaters. Sources of ammonia and nitrate in the wastewater include the use of ammonium-nitrate-fuel oil as a blasting agent, and the use of other nitrogen-containing reagents during processing. The objective of this work was to investigate a biological process for the removal of nitrogenous compounds from real metal-processing wastewater. The system comprised an aerobic continuously stirred tank reactor (CSTR) followed by an anaerobic packed column and was run using real wastewater from a metal-processing operation. The system was inoculated using humus sludge from a municipal trickling filter and a period of approximately four weeks was required for a denitrifying biofilm to develop. Results showed that ammonia removal occurred readily in the CSTR while nitrite oxidation was slower to develop. The CSTR was found to be suitable for ammonia oxidation; up to 89% ammonia removal was achieved. By employing an integrated process comprising nitrification and denitrification, high ammonia removal efficiencies can be obtained. An effluent that is low in ammonia can be obtained with this system with additional carbon introduced after the CSTR. The gravel-packed column reactor was found to be unsuitable for the removal of nitrate in the configuration used (maximum 15% removal efficiency). The critical parameters for denitrification are nitrate concentration, temperature, influent flow rate and mean cell retention time. Nitrate removal did not meet the expectations projected by previous authors' work using synthetic wastewater.
 
CTR and the accumulative hydrogen ion production (Hp) measured prior to, during and after acetate oxidation. The OUR resulting from exogenous activity and Ac (♦) and NHx-N (○) content are also shown.
Article
Titrimetric methods are considered to be useful for the study of biological wastewater treatment processes, particularly those processes that have negligible influence on the dissolved inorganic carbon pool. However, the application of titrimetric methods for studying biological processes that produce/consume carbon dioxide is not straightforward as microbial activity affects the total amount of dissolved inorganic carbon with a proportioned change (determined by pH) in the concentration of every species of inorganic carbon. In this work, the impact of adjustments to the inorganic carbon pool on titrimetric data was assessed by considering a pH-stat titration of heterotrophic carbon oxidation. It was confirmed that at typical operating conditions (pH 7.5 and K(L)a(CO2) similar or equal to 22.5 h(-1)) carbon oxidation causes a marked increase in the rate of carbon dioxide transfer and consequently has impact on titrimetric data. Model simulation was used to quantify the impact for a wide range of operating conditions. It was found that only when a titration is operated at pH > 8 with a K(L)a(CO2) < 10 h(-1) can the interference that results from action of the bicarbonate system be neglected (< 5% error induced). Outside these operating conditions it is suggested that the interference be accounted for by either measurement or modelling of carbon dioxide transfer.
 
Article
Due to the fact that South Africa is a water-scarce country, integrated water resource management based on sound information is essential. Bio-indicators have provided valuable information for water resource management in recent years and have enjoyed increasing popularity. Bio-indicators especially stepped to the forefront with the realisation that aquatic eco-systems are not only a source of water but also deliver several goods and services, as well as being essential for industrial growth and quality of life of many South Africans. This study aimed to quantitatively test two kinds of biomonitoring tools namely diatom-based (SPI and BDI) and macro-invertebrate based (SASS 5) in order to assess their applicability in South African River systems; and whether any additional information can be gained by using the two tools in tandem. The results showed that diatom indices are affected more by changes in water quality than SASS 5, while SASS 5 displayed a higher dependency on habitat quality, as measured by IHAS, than the diatom indices. It is therefore suggested that the two indices be utilised as complementary indicators for integrated assessment of river health. http://search.sabinet.co.za/WebZ/Authorize?sessionid=0&next=ej/ej_content_waters.html&bad=error/authofail.html
 
Article
Copyright: 2007 Water Research Commission A series of lignocellulosic fungi, capable of cellulase and/or xylanase production, were isolated from soil to be used for cellulose degradation and nitrate removal from nitrate-rich wastewater in simple one-stage anaerobic bioreactors containing grass cuttings as source of cellulose. The fungal consortium, consisting of six hyphomycetous isolates, some of which belong to the genera Fusarium, Mucor and Penicillium, was able to remove a significant portion of the nitrate from the treated water. The results were obtained for three bioreactors, i.e. FR, FRp and AFRp, differing in volume and mode of grass addition. Bioreactor AFRp received autoclaved grass, instead of non-autoclaved grass containing natural microbial consortia, as supplied to FR and FRp. Nitrate removal in FR amounted to 89% removal efficiency, while this was 65% and 67% in FRp and AFRp, respectively. The residual chemical oxygen demand (COD) concentration in FR was higher than 600 mg/ℓ, while it was 355 and 379 mg/ℓ in FRp and AFRp, respectively. The similar nitrate removal results for AFRp and FRp indicated that the micro-organisms attached to grass cuttings did not seem to affect the nitrate removal in the reactor. This observation has led to the conclusion that the fungal consortium was, except for being able to degrade cellulose within the grass cuttings, also responsible for nitrate removal from the synthetic nitrate-rich wastewater
 
Chemical composition of feed and treated water during simultaneous biological sul- phate and sulphide removal
Article
A novel chemical/biological process is described in which sulphate and sulphide are removed simultaneously during biological treatment. Partial sulphate removal is achieved during chemical pre-treatment. In the biological stage sulphate is reduced to sulphide in a complete-mixed reactor through addition of sucrose or ethanol as a carbon and energy source. Sulphide is oxidised by allowing oxygen to enter the system in a controlled way. The experimental investigation of the process showed that sulphate and sulphide could be removed simultaneously due to co-existence of sulphate-reducing bacteria and sulphur oxidising bacteria. The volumetric sulphate reduction rate in a complete-mixed reactor, with sucrose as an organic carbon and energy source, amounts to 12.4 g SO4/(ℓ.d). The rate of biological sulphate removal was found to be directly related to the square root of sulphate, COD and VSS concentrations respectively, and inversely proportional to sulphide concentration. The practical value of simultaneous sulphate and sulphide removal is that only one stage is required for removal of both sulphate and sulphide; a conventional completemixed reactor can be used; and sulphate can be removed in a consistent way to below 200 mg/ℓ (as SO4) due to the stability of the process. By combining the biological stage with CaCO3- neutralisation and/or lime pre-treatment, the chemical cost can be reduced. Sulphate, associated with the over-saturated fraction after treatment with CaCO3 or lime, can be removed through gypsum crystallisation. In the integrated sulphate removal process (CaCO3- neutralisation, lime treatment and biological stages), sulphate can be removed from 9 200 mg/ℓ (typical sulphate concentration of coal discard leachate) to 2410 mg/ℓ, 1 230 mg/ℓ and 205 mg/ℓ (as SO4) in the various stages respectively. The chemical cost with the integrated process amounts to R2.94/m3, versus R12.44/m3 when all the sulphate is removed using the biological stage only. Similarly, the cost for treating magnesium sulphaterich mine water amounts to R1.92/m3 for the integrated process, versus R3.11/m3 for biological treatment only.WaterSA Vol.30 (2) 2004: 183-189
 
Article
The product of the biological sulphate reduction is sulphide. High concentrations of molecular H2S(g) can be inhibitory for microbial activity, especially at a reactor pH of 6 to 7. This paper focuses on the effect of high sulphide concentrations on the sulphate reduction rates. The results of three investigations operating a continuous reactor, a column reactor and batch-test reactors have shown that increased sulphide concentrations have resulted in improved biological sulphate reduction. In all instances the reactor pH was kept at 7.5 to 8.5. It was shown that when the sulphide concentration was 700 mg/l in a continuously operated reactor, the sulphate reduction rate was 12 gSO(4)/l(.)d. When operating batch-test reactors the results showed that when the sulphide concentration increased, to 1 400 mg/l, the volumetric and specific sulphate reduction rates correspondingly increased to 4.9 gSO(4)/l(.)d and 1.5 gSO (4)/gVSS, respectively. Thirdly, operating a tall column reactor using H-2 and CO2 as the energy source, showed that when the initial sulphide concentration of the feed water was 0, 100 and 268 mg/l, the average biological sulphate removals were 650, 1 275 and 1 475 mg/l, respectively. These obtained results indicated that the addition of sulphide to the feed water to the reactor had a positive effect on sulphate removal. Improved sulphate removal results in increased alkalinity production and in an increased reactor pH, which in turn is favourable for a decrease in the redox potential, when a dominant redox couple, like sulphate: sulphide, is present in a reactor.
 
The Bot River Estuary and its catchment 
Monthly average flow rate (m³/s) for station G4H014-A01, Roode Heuvel in the Bot River
Summary of mouth breachings: 1979 -2000
Article
For the past 20 years management of the Bot/Kleinmond estuarine system in the south-western Cape has been based on the premise that, barring intervention, the estuary was naturally evolving into a freshwater coastal lake. This paper presents evidence, based on a 20-year series of water-level data, updated runoff estimates from the catchments and dimensional data, that, in the absence of anthropogenic influences, the system is not progressing naturally, but artificially, towards becoming a freshwater system. It is concluded that the increasingly closed state of the Bot Estuary in recent years is most likely due to reduction in runoff from its tributaries and premature artificial breaching of the Kleinmond arm of the system. These findings, coupled with the high conservation importance of the Both River Estuary, suggest that the current management plan needs urgent revaluation and that the two estuaries cannot be managed separately.
 
Article
A World Bank long-term perspective study on Sub-Saharan Africa highlighted the need to build human and institutional capacity in virtually all sectors and countries. In South Africa, establishment of a democratic government in 1994 saw increased emphasis placed on capacity building. This led to the revision of policies and legislation directing human resources development. This emphasis on capacity development is reflected in procurement policies to the extent that it is increasingly difficult to successfully bid for funding from government and parastatal organisations unless there is both a plan and a commitment to capacity building in the previously marginalised sectors. There are currently no guidelines to support researchers in their attempts to support the intentions of legislation and policy. It has been assumed that researchers have the understanding and expertise to effectively promote capacity building. Under such conditions the expectations of research administrators are neither clearly structured nor are they understood by researchers. Not surprisingly, researchers often fail to meet the expectations of administrators. In an attempt to contribute towards developing a structured approach, this paper interprets what is meant by capacity building in the context of research projects. Based on this interpretation, reasonable and unreasonable expectations with respect to the extent to which capacity building can be achieved within a given project duration are discussed. A model is suggested, which would improve understanding and delivery and in doing so, achieve better congruence between expectations and outcomes.
 
Top-cited authors
George Ekama
  • University of Cape Town
David C Le Maitre
  • Council for Scientific and Industrial Research, South Africa
H. du Preez
  • University of Johannesburg
Johan HJ van Vuren
  • University of Johannesburg
T. Viraraghavan
  • University of Regina